[填空题]
Siderite is a mineral containintgoxj7; .s 8mjg iron in ty z0pb/cjt e7)he form of iron (II) carbonate,$FeCO_3 $.
A 15.00 g sample of impure siderite was ground into a fine powder and dissolved in $250.0cm^3$ of hot water, and then filtered to remove the insoluble components. After filtration, a $35.00 cm^3$ sample of the iron solution was analyzed via redox titration using a 0.120 $mol \ dm^{-3}$ solution of potassium dichromate. The balanced redox equation is given below:
$Cr_2O^{2-}_{7(aq)}+14^+_{(aq)}+6Fe^{2+}_{(aq)}\rightarrow2Cr^{3+}_{(aq)}+6Fe^{3+}_{(aq)}+7H_2O_{(l)}$
1. 1.Calculate the theoretical percent composition of iron in a sample of pure siderite or iron (II) carbonate. %
2.If $18.1cm^3$ of dichromate solution is used to titrate the actual iron sample to the equivalence point, calculate the number of moles of iron in the titrated sample. mol
3.Using your value from (ii), determine the mass of iron present in the original sample of siderite. g
4.Using the experimental number of moles of $Fe^{2+}$ found in (ii), calculate the experimental mass of iron carbonate $(FeCO_3)$ in the impure sample and then calculate the percent of impurities found in this sample.Percent impurities %
2.Another iron-containing mineral is a hydrate of iron sulfate,$Fe_x(SO_4)_y ⋅ n H_2O$, pure sample is first heated to drive off all of the water. After heating to a consistent mass, a sample with a mass of 5.250 g is found to have 3.561 g of anhydrous material remaining. The remaining anhydrous material was analyzed and found to have 36.76%,21.11% sulfur, and 42.13% oxygen.
1.Determine the empirical formula of the anhydrate.
2.If the molar mass of the hydrate is determined to be $151.92 gmol^{-1}$, what is the actual formula of the anhydrate?
3.Use the information given in part b(i) to determine the number of moles of water present and, thus, the formula of the hydrate.
